Napredni pristopi sinteze zeolitom podobnih imidazolatov ter njihova karakterizacija

magistrsko delo

Katja Vodlan (Author), Amalija Golobič (Mentor), Matija Strlič (Thesis defence commission member), Anton Meden (Thesis defence commission member), Nataša Zabukovec Logar (Co-mentor)

Abstract

Zaradi hitre rasti svetovnega prebivalstva in klimatskih sprememb se potrebe po ogrevanju in ohlajanju povečujejo. Zato s tem narašča tudi zanimanje za termokemijsko shranjevanje energije, ki ima v primerjavi z ostalimi načini manjše toplotne izgube in lahko doseže bistveno višjo gostoto shranjevanja energije. Deluje na osnovi kemijske reakcije in/ali sorpcije plinov na trdno snov oziroma tekočino. Da je adsorbent ustrezen za uporabo v procesu shranjevanja toplotne energije na osnovi sorpcije, mora imeti ustrezne specifične lastnosti, kot so visoka sorpcijska kapaciteta ter primerna desorpcijska temperatura in temperatura, pri kateri se toplota sprošča. V zadnjih letih se je na tem področju močno povečalo zanimanje za uporabo kovinsko-organskih poroznih materialov (ang. metal-organic frameworks – MOF) in njihove podskupine zeolitnih imidazolatnih ogrodij (ang. zeolite imidazolate frameworks – ZIF), ki imajo veliko specifično površino, različne funkcionalne skupine na ogrodjih in velikost por, ki omogočajo selektivno adsorpcijo delovne tekočine v material. Za njihovo sintezo se kot topilo pogosto uporablja dimetilformamid (DMF), ki ni okolju prijazen in sem ga pri solvotermalni sintezi materialov ZIF-71 in ZIF-93 zamenjala z bolj zelenimi topili, kot so voda, metanol in etanol. Oba materiala sem sintetizirala tudi s pomočjo mehanokemijske sinteze. Za optimizacijo solvotermalne sinteze sem uporabila sintezni postopek iz literature, pri čemer sem sistematično spreminjala različne sintezne parametre (količino in vrsto topila, količino dodane kisline/ baze, vrsto cinkovega prekurzorja in čas trajanja reakcije). S pomočjo različnih metod strukturne karakterizacije-rentgenske praškovne difrakcije, termogravimetrične analize, dušikove fizisorpcije in elektronske vrstične mikroskopije, sem okarakterizirala sintetizirane vzorce. Termogravimetrično metodo sem uporabila tudi za določitev deleža sorbirane vode in etanola v ogrodjih sintetiziranih vzorcev. Čeprav sem uspela čas sinteze zmanjšati iz 18 na 4 ure in pri tem pridobila produkt s primerljivimi lastnostmi, ima produkt ponovljene sinteze pri povišani temperaturi iz literature še vedno najboljše sorpcijske lastnosti. Poleg tega mi je uspelo sintetizirati produkt, pripravljen iz cinkovega nitrata heksahidrata po 5 urah izvajanja sinteze, ki ne potrebuje aktivacije. Solvotermalne sinteze ZIF-71 mi ni uspelo optimizirati, saj ima produkt z najboljšimi karakteristikami med sintetiziranimi vzorci nekoliko manjšo sorpcijsko kapaciteto za etanol kot vzorec, sintetiziran po postopku, opisanem v literaturi. Znanega mehanokemijskega sinteznega postopka za pripravo preiskovanih ogrodij v tem času še ni bilo, zato sem ogrodji poskušala sintetizirati iz različnih razmerij reaktantov in z uporabo različnih topil. Ustrezni sintezni postopek sem v nadaljevanju optimizirala in preverila vpliv različnih sinteznih parametrov, kot so čas in frekvenca mletja, vpliv dodatka različnih količin kisline/baze, na kristaliničnost in fazno sestavo produkta. Produkt mehanokemijske sinteze ZIF-93 ima primerljive lastnosti, kot jih ima produkt solvotermalne sinteze pri sobni temperaturi. Z imenovano metodo mi je uspelo sintetizirati tudi ZIF-71, vendar ta ni uporaben za shranjevanje energije, saj se s sorpcijo etanola in vode, kot testnih delovnih tekočin, pretvori v ZIF-72, ki je slabo porozen.

Keywords

termokemijsko shranjevanje energije;kovinsko-organski porozni materiali;zeolitna imidazolatna ogrodja;zelena topila;solvotermalna sinteza;mehanokemijska sinteza;magistrska dela;

Data

Language:	Slovenian
Year of publishing:	2022
Typology:	2.09 - Master's Thesis
Organization:	UL FKKT - Faculty of Chemistry and Chemical Technology
Publisher:	[K. Vodlan]
UDC:	661.183.6(043.2)
COBISS:	121468931
Views:	48
Downloads:	29
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Advanced approaches to the synthesis of zeolite-like imidazolates and their characterization
Secondary abstract:	The demand for heating and cooling are increasing due to the growing global population and climate change. There is a growing interest in addressing this demand in an environmentally friendly way, one such method is thermochemical energy storage (TCES). TCES has lower heat losses compared to other methods and can achieve a significantly higher energy storage density. TCES is based on the reversible chemical reactions and/or sorption processes of gases in solids or liquids. Potential adsorbents for heat storage applications, are required to have specific properties, such as high sorption capacity, optimum desorption temperature and released heat temperature. In recent years, the interest in using of metal-organic frameworks (MOFs) and their subgroup zeolite imidazolate frameworks (ZIFs), which have a large specific surface area, various functional groups on the surface of frameworks, different pore sizes and therefore enable selective adsorption of the working fluid into the material, has grown significantly in this field. The majority of ZIF synthesis uses dimethylformamide (DMF) as the solvent, which is not environmentally friendly. Therefore, the aim of this research was to replace DMF with greener solvents, such as water, methanol and ethanol in solvothermal synthesis of ZIF-71 and ZIF-93 materials. Both materials were synthesised by using mechanochemical method as well. Initially, the samples were synthesised using methods from literature, these methods were then optimised by changing various parameters (including the amount of solvent, type of solvent, the amount of acid/base added, type of zinc precursor and duration of the reaction). The characterization of the samples was performed using powder X-ray diffraction, thermogravimetric analysis, nitrogen physisorption and scanning electron microscope. Aditionally thermogravimetric method was also used to determine the % ethanol and % water uptake of the optimised ZIF samples. While the synthesis time for ZIF-93 was reduced from 18 hours down to 4 hours with similar properties, the initial synthesised ZIF-93 sample from literature showed the best uptake. Furthermore, ZIF-93 was synthesised from zinc nitrate hexahydrate in just 5 hours, with no activation required. Solvothermal synthesis of ZIF-71 was not optimised, as the product with the best characteristics among the synthesized samples has a slightly lower ethanol sorption capacity than the initial sample, synthesized according to the procedure described in the literature. Currently there are no published procedures for mechanochemical synthesis of the two ZIFs. Therefore, they were synthesized by using different ratios of reactants and type of solvents. Additionally, the best synthesis procedure was optimised and the influence of various reaction parameters, such as the time and frequency of milling, the influence of the addition of different amounts of acid/base... on the crystallinity and phase composition of the product were analysed. The mechanochemically synthesised ZIF-93 sample has comparable properties to the product of solvothermal synthesis at room temperature. ZIF-71 was synthesised by using the named method as well. However, it is not useful for heat storage applications as it was converted into poorly porous ZIF-72 during the water and ethanol sorption studies.
Secondary keywords:	thermochemical energy storage;metal-organic frameworks;green solvents;solvothermal synthesis;mechanochemical synthesis;Univerzitetna in visokošolska dela;
Type (COBISS):	Master's thesis/paper
Study programme:	1000375
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. v Ljubljani, Fak. za kemijo in kemijsko tehnologijo, smer Kemija
Pages:	123 str.
ID:	16279653